Properly implement Debug for Window and EventLoop types (#3297)

For EventLoop, EventLoopBuilder, EventLoopProxy and by requiring it as
a supertrait of Window and ActiveEventLoop.

It is especially useful for user to be able to know that Window is Debug.

src/platform_impl/linux/x11/dnd.rs

@@ -39,6 +39,7 @@ impl From<io::Error> for DndDataParseError {
     }
 }
 
+#[derive(Debug)]
 pub struct Dnd {
     xconn: Arc<XConnection>,
     // Populated by XdndEnter event handler

src/platform_impl/linux/x11/event_processor.rs

@@ -45,6 +45,7 @@ pub const MAX_MOD_REPLAY_LEN: usize = 32;
 /// The X11 documentation states: "Keycodes lie in the inclusive range `[8, 255]`".
 const KEYCODE_OFFSET: u8 = 8;
 
+#[derive(Debug)]
 pub struct EventProcessor {
     pub dnd: Dnd,
     pub ime_receiver: ImeReceiver,

src/platform_impl/linux/x11/ime/mod.rs

@@ -5,6 +5,7 @@ mod context;
 mod inner;
 mod input_method;
 
+use std::fmt;
 use std::sync::mpsc::{Receiver, Sender};
 use std::sync::Arc;
 
@@ -56,6 +57,12 @@ pub(crate) struct Ime {
     inner: Box<ImeInner>,
 }
 
+impl fmt::Debug for Ime {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Ime").finish_non_exhaustive()
+    }
+}
+
 impl Ime {
     pub fn new(
         xconn: Arc<XConnection>,

src/platform_impl/linux/x11/mod.rs

@@ -71,6 +71,7 @@ type X11rbConnection = x11rb::xcb_ffi::XCBConnection;
 
 type X11Source = Generic<BorrowedFd<'static>>;
 
+#[derive(Debug)]
 struct WakeSender<T> {
     sender: Sender<T>,
     waker: Ping,
@@ -91,6 +92,7 @@ impl<T> WakeSender<T> {
     }
 }
 
+#[derive(Debug)]
 struct PeekableReceiver<T> {
     recv: Receiver<T>,
     first: Option<T>,
@@ -127,6 +129,7 @@ impl<T> PeekableReceiver<T> {
     }
 }
 
+#[derive(Debug)]
 pub struct ActiveEventLoop {
     xconn: Arc<XConnection>,
     wm_delete_window: xproto::Atom,
@@ -144,6 +147,7 @@ pub struct ActiveEventLoop {
     device_events: Cell<DeviceEvents>,
 }
 
+#[derive(Debug)]
 pub struct EventLoop {
     loop_running: bool,
     event_loop: Loop<'static, EventLoopState>,
@@ -157,6 +161,7 @@ pub struct EventLoop {
 
 type ActivationToken = (WindowId, crate::event_loop::AsyncRequestSerial);
 
+#[derive(Debug)]
 struct EventLoopState {
     /// The latest readiness state for the x11 file descriptor
     x11_readiness: Readiness,
@@ -762,7 +767,7 @@ impl Deref for DeviceInfo<'_> {
     }
 }
 
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 pub struct EventLoopProxy {
     ping: Ping,
 }

src/platform_impl/linux/x11/window.rs

@@ -39,6 +39,7 @@ use crate::window::{
     WindowAttributes, WindowButtons, WindowId, WindowLevel,
 };
 
+#[derive(Debug)]
 pub(crate) struct Window(Arc<UnownedWindow>);
 
 impl Deref for Window {
@@ -411,6 +412,7 @@ impl SharedState {
 unsafe impl Send for UnownedWindow {}
 unsafe impl Sync for UnownedWindow {}
 
+#[derive(Debug)]
 pub struct UnownedWindow {
     pub(crate) xconn: Arc<XConnection>, // never changes
     xwindow: xproto::Window,            // never changes